A high-pressure mixing head apparatus is sometimes used for formation of, for example, polyurethane foam. Conventionally, there existed a mixing head apparatus with a fixed nozzle design such as the one shown in FIG. 21. FIG. 22 shows a detailed view of a lower part of FIG. 21. In the mixing apparatus of FIGS. 21 and 22, one 5a and the other 5b of two types of chemically reactive component materials 5a and 5b are expelled at high pressure using plungers into a chamber interior 10 from nozzle outlets 80 respectively provided in opposite side walls 11 of the chamber 1 so that both component materials 5a and 5b impinge on and mix with each other. Reference numeral W denotes the point of impingement, 8 denotes nozzle members, 2 denotes an injection piston, and OL denotes oil for the injection piston. A liquid blend 6 (fluid mix) composed of two types of component materials 5 mixed together is discharged from a discharge unit 13 at the bottom of the apparatus into a mold (not shown) so that it is molded and foamed inside the mold.
Accordingly, desirable requirements for the mixing head apparatus were that: (1) the liquid blend 6 is well agitated; and (2) the liquid blend 6 is discharged from a discharge port 14 uniformly and smoothly at a measured blend ratio without scattering or splashing at the start of discharge (hereinafter referred to as “smooth flow”). Attempts have been made to raise the speed of materials traveling through nozzles to obtain a well-agitated liquid blend, which, however, increases the load imposed on the apparatus due to higher pressure of the pump. Also, there is a limit to the pump pressure and an attempt to further increase agitation leads to difficulties in obtaining the smooth flow. Any redundant energy remaining in the liquid blend 6 when it is discharged from the discharge port 14 of the mixing head apparatus makes it difficult to obtain a smooth flow of the liquid blend 6.
For these reasons, to solve such problems, apparatuses shown in FIGS. 23 and 24, or an improved apparatus according to an invention entitled “Apparatus for injecting fluid raw materials of plastic foam”, or an improved apparatus according to an invention entitled “Improved impingement mixing type mixing module” have been proposed so far (see Patent Documents 1 and 2).    Patent Document 1: Japanese Laid-Open Patent Application Publication No. 2003-299939    Patent Document 2: Japanese Laid-Open Patent Application Publication No. 1992-093204